AOC1 and insomnia measurement: Interestingly, a recent study carried out in a sample of 167 adult patients with symptoms of insomnia who underwent genotyping analysis of the four most relevant SNP variants of the AOC1 gene, DAO enzyme deficiency was present in 138 patients, with a prevalence rate of 82.6 % (95 % CI 76–88.1 %) [24].